An American couple who spent 21 years in jail, before being released, are being denied exoneration.

Dan and Fran Keller, who prior to being jailed were day care owners, have spent 21 years behind bars on what now appears to have been flimsy evidence. They were convicted based almost solely on evidence which has since been refuted and for that reason they are now seeking full exoneration and the charges against them be expunged.

The couple were jailed in 1992 on the charge of child abuse involving satanic rituals but were freed last year on bond after the only physical evidence against them was found to be a mistake. The non-physical evidence however appears to be solid, with therapists testifying that they helped three children recover memories of satanic rituals and sexual abuse at an Austin preschool the Kellers operated. Without at least some physical evidence linking the Kellers to the children however there is no grounds for the couple to be kept in prison.

The Kellers have always denied their convictions and are seeking to have the charges thrown out of court, a task they are finding difficult to accomplish. Travis County prosecutors remain unwilling to proclaim them innocent due to the wording of the law. The prosecutors have said to overcome a jury finding of guilt, the courts would require new evidence that “unquestionably establishes innocence”. This means that without physical evidence, something like an ironclad alibi or DNA proof, their convictions will not be “thrown out” as they wish.

“Our responsibility is to make sure the law is properly applied, and, under the applicable standards, we are not satisfied that they have established actual innocence under the law,” Travis County Assistant District Attorney Scott Taliaferro said. Fran Keller has alleged that this standard is unfair saying, “It’s so hard to prove you’re innocent when there was never a crime”, she also bemoaned the fact that it so difficult to prove a negative rather than have evidence to the positive.

In 1992 the Kellers had been sentenced to 48 years in prison. The key piece of physical evidence was from an emergency room doctor who testified that internal lacerations on one child were evidence of abuse. However in court documents filed in 2013, Dr Michael Mouw says that the lacerations in question were, in fact, normal physiology.

That reversal is what led to the Kellers’ release and subsequent pursuit of an exoneration. The claim of innocence will be put to the Texas Court of Criminal Appeals, where a core of conservative judges typically takes a dim view toward overturning jury verdicts. The court will also be led by the recommendations of Senior District Judge Wilford Flowers, who presided over the Kellers’ 1992 trial and their recent appeals, which he has already rejected twice.